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Star explosions may have played a more important role in the history of Earth’s climate than scientists thought.
Close supernovas have left a series of possible fingerprints in the rings of trees here on Earth over the past 40,000 years, potentially disrupting our planet’s climate on several occasions during that time, according to a new study.
“These are extreme events, and their potential effects seem to match the recordings of dark circles,” study author Robert Brakenridge, senior research associate at the Institute of Arctic and Alpine Research at the University of Colorado at Boulder , said in a press release.
Supernova photos: stunning images of star explosions
Brakenridge compiled a list of 18 supernovas – violent explosions that mark the death of certain types of stars – that occurred about 4,900 light years from Earth. He then compared the estimated timing of these cosmic events with carbon-14 peaks, as observed in the dark circles record.
Carbon-14 is a radioactive isotope of carbon that contains eight neutrons in its atomic nucleus instead of the usual six. Carbon-14 is rare on Earth and it does not occur here naturally without outside influence – that is, high energy radiation from deep space, which can convert some of the “normal” carbon in our atmosphere to carbon. -14 (which is why this isotope is also called radiocarbon).
“There is usually a constant amount year over year,” Brakenridge said. “The trees collect carbon dioxide, and some of that carbon will be radiocarbon. “
However, the amount of radiocarbon is not always constant. Scientists have spotted spikes in the dark circles registry, which have typically been attributed to powerful flares from our own sun. But Brakenridge suspected that supernovas might be involved, so he investigated a possible link.
And he found one tantalizing but tentative: Eight of the closest supernovas on his list occurred around the same time as a brief radiocarbon spike. The association was particularly strong for four supernovas, including one 13,000 years ago that ended the life of a star in the constellation Vela about 815 light years from Earth.
Shortly after this explosion, radiocarbon levels briefly rose by about 3% in Earth’s atmosphere, Brakenridge found.
The results are not conclusive, given the various uncertainties involved. For example, it is difficult to date supernovas precisely; the alleged timing of Vela’s explosion could be nearly 1,500 years later, Brakenridge said. But he believes the new findings, which were posted online last week in the International Journal of Astrobiology, show that further research on a supernova-radiocarbon bond is warranted.
“What keeps me going is when I look at the Earth records and say, ‘My God, the predicted and modeled effects seem to be there,’ Brakenridge said.
He’s not the only scientist to suggest that supernovas may have significantly affected life on Earth. Other studies have postulated that nearby star explosions caused or contributed to certain mass extinctions, modifying the atmosphere of our planet and causing climate change.
Mike Wall is the author of “Over there“(Grand Central Publishing, 2018; illustrated by Karl Tate), a book on the search for extraterrestrial life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.
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